Name: building carbon-carbon bonds with grignard reagents
Uploaded: 2023-04-30T06:54:40.000Z
Duration: 7 min 20 s
Channel: JoVE

<img alt="Grignard reaction diagram: alkyl bromide with Mg, THF forming alcohol." src="/files/ftp_upload/10337/10337fig2.jpg" data-altupdatedat="1761830439000" data-alt="Figure 2">
1. Grignard Reagent Formation
<ol>
	<li>Flame-dry a round bottom flask equipped with a magnetic stir bar.</li>
	<li>Add magnesium (Mg, 1.1 equiv.) to the round bottom flask.</li>
	<li>Add a small amount of iodine (I2, a few crystals). Addition of iodine is to help remove any MgO on the surface of the Mg. Removing MgO allows for Mg and the aryl/alkyl halide to come in contact and react. Sonication or addition of methyl iodide or 1,2-dibromoethane can also help with initiation.</li>
	<li>Cool the reaction mixture to 0 °C with an ice-water bath</li>
	<li>Slowly add a THF (1 M) solution of allyl bromide (1 equiv.) to the round bottom flask with magnesium.</li>
	<li>After adding the solution of allyl bromide, stir the reaction mixture for 3 h at room temperature.</li>
</ol>
2. Nucleophilic Addition
<ol>
	<li>In a separate flame-dried round bottom flask, add trans-cinnamaldehyde (0.85 equiv.) and THF (0.5 M with respect to trans-cinnamaldehyde) and cool to 0 °C.</li>
	<li>Slowly add the THF solution of the Grignard reagent (allyl-magnesium bromide) to the trans-cinnamaldehyde solution.</li>
	<li>After the addition, warm the reaction mixture to room temperature by removing the ice-water bath and stir for 4 h.
	<ol>
		<li>Monitor the reaction progress via TLC by looking for the disappearance of trans-cinnamaldehyde.</li>
	</ol>
	</li>
	<li>After reaction completion, cool the mixture to 0 °C with an ice-water bath.</li>
	<li>Slowly quench the reaction with a saturated aqueous solution of ammonium chloride (NH4Cl).</li>
	<li>Transfer the mixture into a separatory funnel and extract the aqueous layer with ethyl acetate 3x.</li>
	<li>Combine the organic layers and wash with water and brine (a saturated aqueous solution of NaCl).</li>
	<li>Dry the organic layer with anhydrous MgSO4, filter, and evaporate the solvent via rotatory evaporation.</li>
	<li>Purify the crude residue via flash column chromatography.</li>
</ol>

This experiment has demonstrated how to synthesize a Grignard reagent from an aryl/alkyl halide and how to use the Grignard reagent to perform a nucleophilic addition onto a carbonyl compound to construct a new carbon-carbon bond.
The Grignard reaction is widely applied in the synthetic chemistry world, and is used in university research labs, national laboratories, and pharmaceutical companies. Simple Grignard reagents are commercially available, but often times unique and specialized Grignar...

grignard reaction

Grignard Reaction

Source: Vy M. Dong and Faben Cruz, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate how to properly carry out a Grignard reaction. The formation of an organometallic reagent will be demonstrated by synthesizing a Grignard reagent with magnesium and an alkyl halide. To demonstrate a common use of a Grignard reagent, a nucleophilic attack onto a carbonyl will be performed to generate a secondary alcohol by forming a new C-C bond.

The purified product should have the following 1H NMR spectrum: 1H NMR &#948; 7.23-7.39 (m, 5H), 6.60 (d, J = 16.0 Hz, 1H), 6.23 (dd, J = 6.4 Hz, 1H), 5.84 (m, 1H), 5.14-5.20 (m, 2H), 4.35 (q, J = 6.4 Hz, 1H), 2.37-2.43 (m, 2H), 1.9 (br s, 1H).

Source: Vy M. Dong and Faben Cruz, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate how to properly carry ...

The Grignard reaction is a useful tool for the formation of carbon-carbon bonds in organic synthesis.This reaction was discovered more than a century ago by a French Chemist named Victor Grignard for which he was rewarded a Nobel Prize in 1912.The Grignard reaction consists of two steps. The first step is reacting an organohalide with magnesium metal, usually present in the form of turnings. This leads to in situ formation of an organomagnesium halide A.K.A. Grignard reagent.The second step is the reaction between this reagent and a carbonyl-containing compound like aldehyde, ketone, or ester, and depending on the compound used, a secondary or tertiary alcohol, composed of organic portions from both the reagent and the carbonyl-containing compound, is produced.In this video, we will show a step-by-step protocol for preparing allylmagnesium bromide, a frequently used Grignard reagent in chemistry labs. This will be followed by the procedure for reacting this reagent with trans-cinnamaldehyde to obtain a secondary alcohol. Lastly, we will look at a couple of applications of this reaction. Prior to addition of the reagents, flame-dry a 50-mL flask and stir bar to remove all traces of

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Organic Chemistry II

building carbon-carbon bonds with grignard reagents

Grignard reagents are useful organometallic compounds for building carbon-carbon bonds. This experiment shows how to make a Grignard reagent from magnesium and an alkyl halide. It then uses that reagent in a reaction with a carbonyl compound.

A nucleophilic attack on the carbonyl is carried out to form a secondary alcohol. This step shows a common use of Grignard reagents in organic synthesis. The reaction demonstrates how a new carbon-carbon bond can be formed during the process.

Building Carbon-Carbon Bonds with Grignard Reagents

building-carbon-carbon-bonds-with-grignard-reagents

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Grignard reagents are useful organometallic compounds for building carbon-carbon bonds. This experiment shows how to make a Grignard reagent from magnesium and an alkyl halide. It then uses that reagent in a reaction with a carbonyl compound. A nucleophilic attack on the carbonyl is carried out to form a secondary alcohol. This step shows a common use of Grignard reagents in organic synthesis. The reaction demonstrates how a new carbon-carbon bond can be formed during the process.

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This collection covers the theory and reactions necessary to carry out syntheses on a more advanced level. In addition, a few videos introduce methods commonly used to analyze the reaction products such as infrared spectroscopy and polarimetry.

Learn how magnesium and an alkyl halide form a Grignard reagent, then how it reacts with a carbonyl to create a secondary alcohol and a new C-C bond.

Building Carbon-Carbon Bonds with Grignard Reagents

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